Due to a security bug (not much detail is available but it seems to be Linux only), a second Firefox 3.6 release candidate was considered necessary and already built. It is is currently in QA process before its public availability some time next week.
According to the latest meeting minutes, Mozilla was considering January 19 for Firefox 3.6 release if the bug didn’t prove to be severe enough. So, final release date will most likely be January 26th, the second possible date, and another Tuesday, Mozilla’s favorite release day! 🙂